The present invention relates to new and improved power driver impact tools, and in particular to a pneumatic- or hydraulically-operated hammer driver for driving fasteners, such as nails into hard substrates, particularly steel plate, or reinforced concrete, or steel plate overlying concrete.
A number of manual and pneumatic or hydraulically-operated impact tools have been designed for driving nails and other forms of impact installed fasteners into hard substrate materials such as metal, concrete, wood, thermo plastics, and other materials, with the fasteners being singly fed from a spring-biased clip magazine mechanism.
As exemplified in U.S. Pat. Nos, 3,711,008; 3,638,532; 3,278,103 and 3,952,398 and more particularly my recent U.S. Pat. No. 4,122,904, such tools generally consist of a guide track in the form of a bore along which a hammer or driver is reciprocated, and a side opening whereby fasteners may be introduced singly into the hammer bore in position to be intercepted and driven by the hammer when the latter undergoes its drive stroke. In essence, a compressed gas or liquid is caused to act upon a piston in order to drive the hammer against the fastener head surface, and thereby impact-installing the fastener into the hard work surface.
While it is technically possible to load the attached fastener supply magazine on a one fastener at a time basis, it is clear that the fastener loading process can be improved and speeded significantly if the fasteners are first pre-assembled in a serially-connected clip arrangement. This utilization of a serially-arranged fastener clip structure would lead to an increased efficiency in the operation of the pneumatic or hydraulic hammer driver tool.
Accordingly, this arrangement of an improved fastener clip structure has been devised and described in my earlier U.S. Pat. No. 4,106,618. This assembly of a plurality of fasteners in the form of a clip in which the fasteners are interconnected serially for both easy handling and installation into the hammer drive tool, leads to the result that on successive cycles of operation of the hammer driver tool, the serially-aligned fastener strip is being advanced by a spring biased mechanism in the attached magazine, thereby inserting or indexing another fastener into the hammer bore, with the resultant impact of the hammer shearing the fastener from the attached strip and driving the fastener into the work surface below.
In many of the prior art magazine fed power driven impact tools, particularly where the fasteners are held together by a connecting strip, there has existed the problem of a tendency for the tool to become jammed during its operation as a result of the fasteners being impacted off center by the hammer, i.e., the fasteners are struck by the hammer before they are centrally positioned in the hammer bore. The latter condition can occur because of a weakness developed by the spring of the fasteneer feeding mechanism of the magazine or because the tool is refired by the operator before a new fastener can be indexed fully into the hammer bore. Impacting the fasteners off center causes them to be canted, i.e., directed downward at an angle to the central axis of the hammer bore. One problem that may be caused by the canting action is a reduction of the impact velocity imparted to the fastener, with the attendant consequence being that the fastener is unable to penetrate the hard work surface or penetrates it only part way. However, particularly in the utilization of fasteners where they are gripped by a connecting strip over only a short portion of their length, there arises the likelihood of a greater detriment-fastener jamming within the hammer bore following the impact imparted to the fastener by the hammer. If the fastener is not centrally seated in the hammer bore prior to the hammer impact, on impact by the hammer the fastener tip will be deflected towards the magazine side of the hammer bore wall with the attendant jamming of the tool.
The present invention has overcome this previously major problem by incorporating between the fastener magazine and the tool foot portion a face plate anti-jamming device that provides a recess which forms part of the hammer bore, along with an integrally designed inclined fastener guide groove surface that functions to restore a vertical direction of travel to a canted impact-driven fastener, thereby eliminating the previously described jamming tendency of the driver tool. In the event that the fastener is impacted while being in an offset position from the impact surface of the hammer head, the fastener may tend to travel in an angular direction not coaxial with the hammer bore. Because of the fact that the fastener is still coupled to the strip of fasteners when it is struck by the hammer, it will tend to be canted so that its tip is directed toward the magazine. In such event the tip of the fastener will, in its downward and deflected path of travel, emerge through the recessed hammer bore section of the present invention face plate and encounter the surface of the inclined semi-cylindrical fastener guide groove. Sliding contact of the fastener tip with the fastener guide groove surface results in a "camming action" being imparted to the tip of the descending fastener, whereby it is realigned with the hammer bore and driven out of the tool into the impact work surface.